| 摘要 |
A polyester film for use in a solar cell. Said polyester film is biaxially oriented and contains a polyester consisting primarily of ethylene terephthalate. The sum of the molar proportion of non-terephthalic-acid copolymerization components relative to the total acid content of the aforementioned polyester and the molar proportion of non-ethylene-glycol copolymerization components relative to the total alcohol content of the polyester is between 1.5% and 3.0%, inclusive. The glass transition temperature (Tg) of this film, as determined by differential scanning calorimetry (DSC), is between 74°C and 77°C, inclusive. This film has a weight-average molecular weight between 40,000 and 61,000, inclusive, and a terminal-carboxyl-group concentration between 6 and 29 eq./ton, inclusive. The lengthwise and widthwise thermal contraction percentages exhibited by this film when heat-treated for 30 minutes at 150°C are both between −0.3% and 1.2%, inclusive. This film excels in terms of resistance to hydrolysis, long-term heat resistance, and dimensional stability. |
